1. Field of the Invention
The present invention relates to a disk supporting device, particularly to a disk supporting device capable of holding, for a disk cartridge to be applied to an optical disk apparatus, the disk effectively within the cartridge while the apparatus remains out of use.
2. Related Art
As a case to store a disk or a memorizing medium of an optical disk apparatus, a cartridge has been used to prevent the information surface of the disk from being soiled during handling.
The cartridge is constructed such that a clearance is placed between a disk and cartridge to prevent the disk, when rotating, from contacting with the stationary cartridge. This clearance is insured by an elevating mechanism of a spindle motor which adjusts the height of disk. While the apparatus is switched off, the spindle motor is removed from the disk, and thus the disk falls from gravity to settle at a position where it contacts with the cartridge.
As described above, as the height of disk changes according to whether the apparatus is put into action or is kept out of action, interactions of the disk with other components pose a problem.
More particularly, an interaction with an optical head forms one of such problems.
The optical head must be close to the disk when in use, but it must be kept at a low position when out of use by some means, because the optical head would interfere with the stable positioning of disk when the apparatus is out of use, as long as it remains at a position where it can contact with the cartridge.
As an example of a cartridge capable of supporting a disk therein during switching-off of the apparatus, the cartridge disclosed in Japanese Unexamined Patent Publication No. 64-19572 may be cited which is represented by FIGS. 8 and 9.
With the conventional apparatus as represented in FIGS. 8 and 9, a disk 52 is pushed by one end of a blade 53 which is rotatably placed around a central pivot 61 in a cartridge 51 so that the disk is immobilized being pressed against the inner wall 51B of cartridge which has an annular form. A means to enhance the pressing force is represented by a spring 60. A mark 54 represents a guide slit, and another mark 54a a guide pin. A third mark 55 represents a pressing roller.
During operation, when a shutter 56 is opened, a pin 56a fixed to the shutter 56 engages with a groove 53a of the blade 53 on the opposite end to the pressing end, thereby to spin the blade 53 and to release the disk from the state of being immobilized.
As seen from this example, many of the conventional disk holding devices aim mainly at protecting the disk from external mechanical shocks during switching-off, and consist simply of immobilizing a disk by pressing its outer rim against some hard thing.
Namely, the conventional device as represented by FIGS. 8 and 9 mainly aims at preventing the read/write performance of a disk from being degraded as a result of damages due to vibrations, or from adherence of dusts onto the disk surface, while the cartridge is being carried from one place to another by hand. Thus, the conventional device is not produced after a due attention has been paid to thinning of the device as a whole.
To develop a new disk device, it is most important to pay close attention to making the device as small and thin as possible so that it has an excellent portability. Thus, it has been desired to make a clearance between the optical head and disk in the cartridge as small as possible when the cartridge is loaded.
The relative position between a cartridge base 51A and a disk 52 of a conventional apparatus is shown for both cases where the apparatus is put to use (FIG. 10A), and the apparatus is put out of use (FIG. 10B).
With the conventional cartridge 51 here concerned, a disk 52 takes a position "a" as represented in FIG. 10A so that a predetermined clearance is insured between the level at which the disk will rotate and the cartridge base 51A in order to ensure smooth rotation of the disk 52. On the other hand, the disk 52 takes a position "b" as represented in FIG. 10B when the apparatus is put out of use. Then, if an optical head takes a position as represented in FIG. 10B, and the cartridge 51 is loaded, the disk will be displaced towards right from the position "b", and hit against the optical head 60.
To prevent this inconvenience, when the cartridge is inserted, it is necessary to lower the optical head 60 sufficiently so that the head may not contact with the disk 52. This makes it necessary to add an extra thickness to the height of cartridge (to accommodate the lowering of head). Further, ascending or descending the optical head unnecessarily frequently makes an optical head supporting mechanism vulnerable to long use and worsens its endurance.
The distance between the optical head (not illustrated here) and disk 52 is determined by the focusing distance of lens. As the disk has a larger capacity and achieves a higher density recording, the focusing distance of lens will become shorter, and the distance between the optical head 60 and disk 52 will be smaller. Therefore, because the clearance is close in magnitude to the focusing distance of optical head, an interaction between the disk and optical head will arise when the cartridge is loaded as long as the disk takes the position "b" as shown in FIG. 10B.